Leak-resistant dry cell



NOV. 29, 1966 T RElLLY ET AL 3,288,650

LEAK-RESISTANT DRY CELL Filed May 1, 1961 INVENTORS THOMAS A. REILLY JOHNSON R. BECKMAN 8"" 3' HA RY K.B|SHOP Brjl94 AT'TOPNFY United StatesPatent Ofifice Patented Nov. 29, 1966 3,288,650 LEAK-RESISTANT DRY CELL Thomas A. Reilly, Johnson R. Beckman, and Harry K. Bishop, Cleveland, Ohio, assignors to Union Carbide Corporation, a corporation of New York Filed May 1, 1961, Ser. No. 106,766 Claims. (Cl. 136-107) This invention relates to leak-resistant dry cells of the type having a closed container surrounding the cell proper.

The socalled Leclanch dry cell used for flashlights, portable radios, photofiash and other devices has gone through an evolution of improvements during the past decade or more inan attempt by manufacturers to prevent leakage from the cell during and after its use. Despite the many proposals, however, that have been advanced, there still remains a need for a better leak-resistant dry cell.

One proposal that has been adopted commercially is to encase a conventional dry cell within a closed container. This dry cell construction, however, has been plagued by certain difiiculties. For example, one type of container that has been used is composed of metal. Althrough this type of container is strong and rugged, it nevertheless suffers from the disadvantage that the metal is subject to corrosion by liquid exudate from the cell. To avoid this disadvantage, non-corrodible containers have also been utilized. The principal difficulty, however, with noncorrodible containers is that they do not possess the strength of metal containers and suffer from the disadvantage that they may often be damaged, and even destroyed, by the pressure which builds up from the formation of gas within the cell. Several suggestions have been advanced for overcoming this disadvantage of noncorrodible containers in which the attempt has been made to continuously vent the gas from the cell. Thus, in prior constructions, the gas has been vented, for example, through the carbon electrode, and then out through venting means provided in the top closure of the container. The difiiculty with these suggestions is that the venting paths, for instance, through the carbon electrode, have been prone to obstruction by cell exudate, thereby blocking the passage of gas from the cell.

In addition to obstructing the venting paths provided in the cell, this cell exudate has also given rise to other serious problems. For example, one diflicult problem has been the tendency for metal formed in solution by normal consumption of the metal electrode to deposit out from the cell exudate in the form of spongy tree-like deposits. These metal deposits have formed principally on top of the depolarizer mix between the electrodes of the cell and have been particularly troublesome from the standpoint of cell performance, for they very likely can short out the cell by establishing short-circuit paths between the cell electrodes. Thus, the cell in many instances may be drained of its power even though it is not in use.

It is therefore an important object of the invention to provide an improved gas venting path in a leak-resistant dry cell of the type having a non-corrodible container, which gas venting path is not prone to obstruction during use of the cell.

More specifically, it is another object to provide such a gas venting path in a leak-resistant dry cell While at the same time preventing the establishment of short-circuit paths between the electrodes of the cell.

Still another object is to provide such a gas venting path in a leak-resistant dry cell particularly of the type of construction utilizing a plastic container.

Briefly, these and other objects are achieved by the invention which comprises a plastic container for a leakresistant dry cell having a top closure provided with a tubular sleeve member surrounding but spaced from the carbon electrode and embedded within the depolarizer mix of the cell defining a barrier which protects the carbon electrode from contact by liquid cell exudate and also providing a path for venting gas from the cell.

In the accompanying drawing:

FIG. 1 is a vertical elevation partially in section of a leak-resistant dry cell embodying the invention;

FIG. 2 is a similar view of the top portion only of a dry cell showing another embodiment of the invention; and

FIG. 3 is a similar view of the bottom portion only of a dry cell showing still another embodiment of the invention.

Referring to the drawing, a leak-resistant dry cell of a construction otherwise conventional but embodying the invention is shown in FIG. 1. The cell comprising a cup electrode 10 of a consumable metal, for instance, zinc, having therein a central electrode 12 of porous carbon embedded within a depolarizer mix 14 and an immobilized electrolyte 16 suitably in the form of a conventional paste, is provided with a molded plastic container 18. The container 18 has integrally molded side walls and a top closure 20 having an integrally formed substantially tubular sleeve member 22, the upper edges of which are substantially V shaped forming a flange fitted tightly around the carbon electrode 12 and supporting a metallic cap 24 having a vent 26 fitted over the top of the carbon electrode 12. The tubular sleeve member 22 surrounds but is spaced from the carbon electrode 12 and is embedded at its lower edges within the depolarizer mix 14 at the junction 28, defining a free space 30 between the tubular sleeve member 22 and the carbon electrode 12 and an exudate chamber 32 between the tubular sleeve member 22 and the side Walls of the container 18.

The bottom closure for the cell comprises a molded plastic disc 34 locked in engagement at its outer peripheral edges with the container 18. A metallic rivet 36 is positioned within the plastic disc 34 and makes contact between the bottom of the cup electrode 10 and a metallic bottom plate 38. The rivet 36 is preferably composed of a non-corrodible and non-consumable type of metal, for example, titanium, chromium or lead as substantially disclosed and claimed in our copending application, Serial No. 106,762, filed concurrently herewith and now abandoned.

As shown in FIGS. 2 and 3, the invention is applicable to a number of dry cell constructions. For example, in FIG. 2, a dry cell is shown utilizing a top closure comprising an annular disc 40 having an intgerally formed tubular sleeve member 22 as illustrated in FIG. 1, the outer peripheral edges of which are locked in engagement with the upper edges of the container 18. Also, as shown in FIG. 3, a dry cell may be constructed with a molded plastic container 42 having integrally molded bottom and side walls. A carbon or graphite button 44 preferably of the type disclosed in our above-referred to copending application is positioned within the bottom of the container 42 and makes contact between the cup electrode 10 and a metallic bottom plate 46. The bottom plate 46 differs from that shown in FIG. 1 in that it is provided with outwardly flanged peripheral edges 48 which lock into the bottom of the container 42.

Having described the construction of a dry cell embodying the invention, its mode of operation may now be visualized. During use of the cell, especially under severe conditions, gas is released. The gas follows a path through or around the carbon electrode 12 in the depolarizer mix 14, into the free space 30 and then through the porous carbon electrode 12, or directly through the electrode 12 from Within the depolarizer mix 14, and then out of the cell through the vent 26 in the metallic cap 24. At the same time, liquid is exuded through the depolarizer mix 14 towards the cup electrode and eventually collects within the exudate chamber 32 but is barred from entering the free space 30 by the tubular sleeve member 22. The junction 28 provides a barrier which effectively blocks off liquid exudate from creeping into the free space 30 over the top surface of the depolarizer mix 14. Thus, it will be seen by this construction that liquid exudate is not only barred from blocking the passage of gas through the free space 30 and the carbon electrode 12 or from escaping out of the cell by way of the free space 30, but also is barred from contacting the carbon electrode 12 and from establishing shortcircuit paths between it and the cup electrode 10 by the deposition of spongy Zinc metal over the depolarizer mix 14. This construction also takes advantage of an insoluble salt layer which normally forms on the surfaces of the depolarizer mix 14 during discharge of the cell. The salt layer actually forms a seal around the junction 28 which liquid exudate cannot penetrate.

A number of dry cells embodying the invention have been made and tested over a wide range of conditions. These tests demonstrated the effectiveness of the invention, for cells otherwise identical'but lacking the structural features of the invention showed evidence of leakage from and/or bulging of the cell container, while those cells embodying the invention showed little or no evidence of gas pressure buildup and consistently demonstrated superior leakproofness. The effectiveness of the invention was further demonstrated by the fact that the dry cells of the invention had a longer life and did not short out during the tests.

It will be understood that numerous variations and modifications of the various constructions described herein may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. A leak-resistant dry cell comprising, in combination, a cup electrode of a consumable metal contaning depolarizer mix, electrolyte and a carbon electrode embedded within said depolarizer mix; and a plastic container encasing said cup electrode having a top closure provided with gas venting means therein, said top closure fitting tightly around said carbon electrode and having an integrally formed substantially tubular sleeve member surrounding but spaced from said carbon electrode providing a free space between said tubular sleeve member and said carbon electrode and an exudate chamber surrounding said tubular sleeve member, said tubular sleeve member being embedded within said depolarizer mix and defining a barrier which protects said carbon electrode from contact by liquid exudate from said cell, said tubular sleeve member in conjunction with said gas venting means in said top closure providing a path for venting gas from said cell.

2. A leak-resistant dry cell as defined by claim 1 in which said top closure comprises a plastic disc locked in engagement with the side walls of said container.

3. A leak-resistant dry cell as defined by claim 1 in which said container is provided with a bottom closure comprising a plastic disc locked in engagement with the side walls of said container, a metallic cover plate positioned to the bottom of said disc and an electrical contact element positioned within said disc and making electrical contact between said cup electrode and said cover plate.

4. A leak-resistant dry cell as defined by claim 1 in which said container comprises integrally formed side walls and a bottom provided with a metallic cover plate and in which an electrical contact element is positioned within the bottom of said container making electrical contact between said cup electrode and said cover plate.

5. A leak-resistant dry cell comprising, in combination, a cup electrode of a consumable metal containing depolarizer mix, electrolyte and a carbon electrode embedded within said depolarizer mix, said carbon electrode extending above said depolarizer mix at the upper end thereof; and a plastic container encasing said cup electrode having a top closure provided with gas venting means therein, said top closure fitting tightly around said carbon electrode at said upper end thereof and having an integrally formed substantially tubular sleeve member surrounding but spaced from said carbon electrode providing a free space between said tubular sleeve member and said carbon electrode and an exudate chamber surrounding said tubular sleeve member, the surface of said carbon electrode at said upper end thereof-being substantially entirely exposed within said free space, said tubular sleeve member being embedded within said depolarizer mix and defining a barrier which protects said carbon electrode from contact by liquid exudate from said cell, said tubular sleeve member in conjunction with said gas venting means in said top closure providing a path for venting gas from said cell.

References Cited by the Examiner UNITED STATES PATENTS 2,198,423 4/1940 Anthony 136-133 2,696,514 12/1954 Bernot 136-133 2,850,558 9/1958 Urry 136133 3,051,769 8/1962 Jammet 136133 3,090,824 5/1963 Reilly et a1. 136133 X 3,115,429 12/1963 Reilly et al 136-133 X FOREIGN PATENTS 1,239,964 7/1960 France.

869,875 6/1961 Great Britain.

JOHN H. MACK, Primary Examiner.

JOHN R. SPECK, JOSEPH REBOLD, Examiners.

S- P RKE W. VAN SISE, Assistant Examiners. 

1. A LEAK-RESISTANT DRY CELL COMPRISING, IN COMBINATION, A CUP ELECTRODE OF A CONSUMABLE METAL CONTAINING DEPOLARIZER MIX, ELECTROLYTE AND A CARBON ELECTRODE EMBEDDED WITHIN SAID DEPOLARIZER MIX; AND A PLASTIC CONTAINER ENCASING SAID CAP ELECRODE HAVING A TOP CLOSURE PROVIDED WITH GAS VENTING MEANS THEREIN, SAID TOP CLOSURE FITTING TIGHLY AROUND SAID CARBON ELECTRODE AND HAVING AN INTEGRALLY FORMED SUBSTANTIALLY TUBULAR SLEEVE MEMBER SURROUNDING BUT SPACED FROM SAID CARBON ELECTRODE PROVIDING A FREE SPACE BETWEEN SAID TUBULAR SLEEVE MEMBER AND SAID CARBON ELECTRODE AND AN EXUDATE CHAMBER SURROUNDING SAID TUBULAR SLEEVE MEMBER, SAID TUBULAR SLEEVE MEMBER BEING EMBEDDED WITHIN SAID DEPOLARIZER MIX AND DEFINING A BARRIER WHICH PROTECT SAID CARBON ELECTRODE FROM CONTACT BY LIQUID EXUDATE FROM SAID CELL, SAID TUBULAR SLEEVE MEMBER IN CONJUNCTION WITH SAID GAS VENTING MEANS IN SAID TOP CLOSURE PROVIDING A PATH FOR VENTING GAS FROM SAID CELL. 